One-dimensional Bargaining with Markov Recognition Probabilities

We study a process of bargaining over social outcomes represented by points in theunit interval. The identity of the proposer is determined by a general Markov process and the acceptance of a proposal requires the approval of it by all the players. We show that for every value of the discount factor below one the subgame perfect equilibrium in stationary strategies is essentially unique and equal to what we call the bargaining equilibrium. We provide a general characterization of the bargaining equilibrium. We consider next the asymptotic behavior of the equilibrium proposals when the discount factor approaches one. We give a complete characterization of the limit of the equilibrium proposals. We show that the limit equilibrium proposals of all the players are the same if the proposer selection process satisfies an irreducibility condition, or more generally, has a unique absorbing set. In general, the limit equilibrium proposals depend on the partition of the set of players in absorbing sets and transient states of the proposer selection process. We fully characterize the limit equilibrium proposals as the unique generalized fixed point of a particular function.This function depends in a simple way on the stationary distribution related to the proposer selection process. We compare the proposal selected according to our bargaining model to the one corresponding to the median voter theorem.microeconomics ;

On the Asymptotic Uniqueness of Bargaining Equilibria

This note reexamines the connection between the asymmetric Nash bargaining solution and the equilibria of strategic bargaining games. Several papers in the literature obtain the asymmetric Nash bargaining solution as the unique limit of subgame perfect equilibria in stationary strategies when the breakdown probability approaches zero. This note illustrates by means of two examples that this result depends crucially on the differentiability of the boundary of the set of feasible payoffs. In the first example the game has a unique stationary subgame perfect equilibrium that fails to converge to the asymmetric Nash bargaining solution. In the second example the game has two stationary subgame perfect equilibria that converge to two distinct limits as the breakdown probability vanishes. This example demonstrates that without differentiability of the set of feasible payoffs there is not even asymptotic uniqueness of stationary equilibria in the bargaining model.microeconomics ;

Majority Rule Dynamics with Endogenous Status Quo

We analyze a stochastic bargaining game in which a new dollar is divided among committee members in each of an infinity of periods. In each period, a committee member is recognized and offers a proposal for the division of the dollar. The proposal is implemented if it is approved by a majority. If the proposal is rejected, then last period’s allocation is implemented. We show existence of equilibrium in Markovian strategies. It is such that irrespective of the initial status quo, the discount factor, or the probabilities of recognition, the proposer extracts the entire dollar in all periods but the initial two. We also derive a fully strategic version of McKelvey’s (1976), (1979) dictatorial agenda setting, so that a player with exclusive access to the formulation of proposals can extract the entire dollar in all periods except the first. The equilibrium collapses when within period payoffs are sufficiently concave. Winning coalitions may comprise players with high instead of low recognition probabilities, ceteris paribus.

Non-cooperative Support for the Asymmetric Nash Bargaining solution

Our work contributes to the game-theoretic analysis of bargaining by providing additional non-cooperative support to the well-known Nash bargaining solution. In particular, in the present paper we study a model of non-cooperative multilateral bargaining with a very general proposer selection protocol and set of feasible payoffs. In each period of the bargaining game, one out of n players is recognized as the proposer according to an irreducible Markov process. The proposer offers a particular element of the convex set of feasible payoffs. If all players accept the offer, it is implemented. If a player rejects the offer, with some probability the negotiations break down and with the remaining probability the next period starts. We show that subgame perfect equilibria in stationary strategies exist and we fuly characterize the set of such equilibria. Our main result is that in the limit, as the exogenous risk of breakdown goes to zero, stationary subgame perfect equilibrium payoffs converge to the weighted Nash bargaining solution with the stationary distribution of the Markov proposer selection process as the weight vector.operations research and management science;

On the asymptotic uniqueness of bargaining equilibria

The paper studies the model of multilateral bargaining over the alternatives representedby points in the mâdimensional Euclidean space. Proposers are chosen randomly and the acceptance of a proposal requires the unanimous approval of it by all the players. The focus of the paper is on the asymptotic behavior of subgame perfect equilibria in pure stationary strategies (called bargaining equilibria) as the breakdown probability tends to zero. Bargaining equilibria are said to be asymptotically unique if the limit of a sequence of bargaining equilibria as the breakdown probability tends to zero is independent of the choice of the sequence and is uniquely determined by the primitives of the model. We show that the limit of any sequence of bargaining equilibria is a zero point of the soâcalled linearization correspondence. The asymptotic uniqueness of bargaining equilibria is then deduced in each of the following cases: (1) m = n−1, where n is the number of players, (2) m = 1, and (3) in the case where the utility functions are quadratic, for each 1 ≤ m ≤ n−1. In each case the linearization correspondence is shown to have a unique zero. Result 1 hasbeen established earlier in Miyakawa and Laruelle and Valenciano. Result 2 is subsumed by the result in Predtetchinski. Result 3 is new.microeconomics ;

One-dimensional bargaining with unanimity rule

The paper examines bargaining over a one--dimensional set of social states, with a unanimity acceptance rule. We consider a class of delta-equilibria, i.e. subgame perfect equilibria in stationary strategies that are free of coordination failures in the response stage.We show that along any sequence of delta-equilibria, as delta converges to one, the proposal of each player converges to the same limit. The limit, called the bargaining outcome, is uniquely determined by the set of players, the recognition probabilities, and the utility functions, and it is independent of the choice of the sequence. We characterize the bargaining outcome as a unique solution of a characteristic equation.mathematical economics;

A Theory of coalition Bargaining

When voting takes place in democratic institutions, we find (either explicitly or implicitly) that there is an agenda setter or a formateur. Such players are uniquely able to make substantive proposals for given topics. Their statuses remain intact even after rejection of proposals, but they must revise rejected proposals constructively (e.g. towards a compromise). We model this in a general environment, show that the equilibrium outcome is generically unique, and characterize it explicitely. The equilibrium outcome is robust to (partially) binding communication between the formateur and the voters. As illustrations, we consider majority bargaining about a cake (leaned on Baron and Ferejohn,1989),where the formateur ends up being a perfect dictator, and a model of legislative voting (leaned on Jackson and Moselle,2002), where he is a dictator if his ideological position is within the quartiles of the parliament. In these cases, our model implements (reversed) McKelvey majority path. Depending on the valuations, the formateur´s power may be weakened when parliamentary decisions can be revised, as this may faciliate tacit collusion amongst the voters. --coalitional bargaining,legislature,non-cooperative

Dynamic Legislative Policy Making

We prove existence of stationary Markov perfect equilibria in an infinite-horizon model of legislative policy making in which the policy outcome in one period determines the status quo in the next. We allow for a multidimensional policy space and arbitrary smooth stage utilities. We prove that all such equilibria are essentially in pure strategies and that proposal strategies are differentiable almost everywhere. We establish upper hemicontinuity of the equilibrium correspondence, and we derive conditions under which each equilibrium of our model determines a unique invariant distribution characterizing long run policy outcomes. We illustrate the equilibria of the model in a numerical example of policy making in a single dimension, and we discuss extensions of our approach to accommodate much of the institutional structure observed in real-world politics.